We are using a solubility assay at high phosphate concentration to determine whether artificial hemoglobins A and S are different from each other. We have changed the central metal in the porphyrin of the heme group in both hemoglobins and are studying the effects of high phosphate on these reconstituted hemoglobins. These studies will allow us to determine whether any of our recent findings of subtle, but significant, conformational changes in copper, zinc, nickel and protoporphyrin IX hemoglobins A affect the solubility of this or the reconstituted hemoglobin S form. This information is relevant to understanding the molecular mechanisms of hemoglobin aggregation, especially for sickle cell hemoglobin.